This invention relates to an improved iron-based casting alloy having improved combinations of toughness, abrasion resistance and corrosion resistance, and the invention also relates to a process for making the alloy.
There are many applications for which it is desirable to have iron-based alloys that are castable and have improved combinations of toughness, abrasion resistance and corrosion resistance. For example, the paper making industry casts refiner plate alloys which can advantageously increase production at faster speeds. However, at these faster speeds, the cast refiner plates wear faster and are more susceptible to brittle fracture.
Cast alloys of iron, chromium, vanadium, niobium, and tungsten have previously been studied by A. Sawamoto et al. as set forth in the Transactions of American Foundrymen""s Society, 1986, pages 403-416. While this experimental work studied these alloy systems, the investigations did not optimize the micro-structure to provide tougher, more wear and corrosion resistant alloys.
One object of the present invention is to provide an improved iron-based casting alloy having improved combinations of toughness, abrasion resistance and corrosion resistance.
In carrying out the above object, the casting alloy of the invention includes an iron matrix having primary carbides (MC) selected from vanadium carbides, niobium carbides, titanium carbides, and combinations of these carbides with substantially no eutectic MC carbides. The alloy also includes eutectic chromium carbides (M7C3) with substantially no primary chromium carbides.
The alloy may also include proeutectic austenite that forms before eutectic austenite that forms with the eutectic chromium carbide.
Another object of the present invention is to provide an improved process for making an iron-based castable alloy having improved combinations of toughness, abrasion resistance and corrosion resistance.
In carrying out the immediately preceding object, the process for making the casting alloy is performed by precipitating in an iron matrix primary carbides (MC) of vanadium carbides, niobium carbides, titanium carbides, or combinations thereof, and by forming eutectic chromium carbides (M7C3) and eutectic austenite without forming any substantial amount of primary chromium carbides.
It is also possible for the process to be performed by precipitating proeutectic austenite before forming the eutectic chromium carbides and eutectic austenite.
The objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when considered with the accompanying drawings.